The present invention generally relates to an apparatus for recording an image on a paper sheet or similar recording medium by using an electrophotographic procedure and, more particularly, to a cartridge loaded with various process units which need periodic replacement, e.g., a charger, developing unit and cleaning unit and removably installed in the body of an electrophotographic apparatus.
An electrophotographic copier, facsimile machine, laser printer or similar apparatus implemented by an electrophotographic process is extensively used. This kind of apparatus includes an image carrier in the form of a photoconductive element. Arranged around the photoconductive element are process units such as a charger, writing unit, developing unit, image transferring unit, and cleaning unit. After the charger has uniformly charged the surface of the photoconductive element to a predetermined polarity, the writing unit writes a desired image in the photoconductive element. Then, the developing unit develops the image on the photoconductive element to produce a visible image. The visible image is transferred by the transferring unit to a paper sheet. The cleaning unit cleans the surface of the photoconductive element after such image transfer. Subsequently, the charger again charges the surface of the photoconductive element to prepare it for another photographic cycle.
A problem with the prior art apparatus of the type described is that the individual process units and parts thereof cannot be replaced, repaired or cleaned unless they are attached and detached one by one each time. When the photoconductive element, among others, is to be replaced, the various process units arranged therearound have to be removed one by one and, after the replacement, mounted again one by one. Moreover, in the event when the process units, especially the developing unit, are mounted and dismounted or when the photoconductive element is replaced, a developer is apt to be scattered around from the developing unit or the photoconductive element. In light of this, it has been proposed to mount the process units which are expendable supplies in a single casing or cartridge, as disclosed in Japanese Patent Laid-Open Publication (Kokai) Nos. 62-165670 and 61-118770 by way of example. Specifically, this prior art scheme mounts a photoconductive drum on the body of an electrophotographic copier or similar apparatus while mounting the charger, developing unit, cleaning unit and other process units on a single cartridge. The cartridge is replaced when the developing unit runs out of toner or when the charger or the cleaning unit fails.
An electrophotographic apparatus may be implemented by a developing unit including a developing sleeve and an agitator, and a developer container loaded with a toner or similar developer and removably mounted on the developing unit, as also proposed in the past. This prior art implementation, however, has a problem that at the time of replacement of the developer container the toner is apt to fall through a toner supply opening of the container to contaminate the interior of the apparatus.